• Journal of Broadcast Engineering
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• v.22 no.5
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• pp.560-569
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• 2017

Recently as the studies on the combined delivery over multiple transmission media are progressed, studies using MMT which is next-generation multimedia transport standard are underway. They are about transmitting video data layered by SHVC through broadcasting network and communication network based on MMT. However, it is difficult to serve synchronized UHD contents in heterogeneous network environment based on MMT, because MMT standard doesn't fully specify the information to indicate the relationship between media. Also, the service that we want to propose in this paper is a broadcasting-based service such as terrestrial broadcasting. Therefore the user must be able to watch various contents continuously. However, the MMT PI(Presentation Information) that controls the spatio-temporal layout of a content has been described as providing only one content. In this paper, we propose the structure of MXD document and MMT PI to provide continuous UHD contents service based on heterogeneous network.

• Journal of KIISE:Information Networking
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• v.37 no.2
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• pp.109-121
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• 2010

Recently, the military of Korea has been establishing the next generation wireless tactical communication system so called Tactical Information Communication Network (TICN). A routing protocol for TICN transport networks has to be able to select a path with high survivality, reliability, and stability while accommodating as many flows as possible with minimum QoS guarantees. The OSPF(Open Short Path First) used widely is determined to be the routing protocol for TICN. With the typical deployment practices OSPF, however, it cannot satisfy the requirements of TICN. In this paper, we propose a cost function for OSPF and a way to tune the OSPF protocol parameters for the TICN transport networks. Through simulations, it is shown that the OSPF with the proposed cost function provides better performance than the OSPF in terms of both the services provided to the applications and the network resources utilization.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.2
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• pp.83-90
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• 2000

In this paper, a stacked circular-disk microstrip 1${\times}$4 array antenna was designed and manufactured and tested to apply in next generation mobile communication, on IMT-2000 system(up-link: 1.885 GHz∼2.025 GHz, down-link: 2.11 GHz∼2.2 GHz) base station which has dual frequency, broadband and high-gain characteristics. The experimental results are as follows : resonant frequency of 1.885 GHz and 2.178 GHz VSWR (1.064 , 1.432), return loss (-30.19 dB , -24.99 dB), band width (VSWR<2) are 402 MHz, -3dB beam width at radiation pattern are ${\alpha}$E-16.8$^{\circ}$, ${\alpha}$H-69$^{\circ}$(1.885 GHz) and ${\alpha}$E-l5.2$^{\circ}$, ${\alpha}$H-51.5$^{\circ}$(2.178 GHz), gain(13.7 dBi∼15.21 dBi).

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.7
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• pp.1597-1601
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• 2013

Multiple antenna technique is attracting attention as a core technology for next-generation mobile communication systems to accommodate explosively increasing mobile data traffic. Especially, recent researches focus on multi-user multiple input multiple output (MU-MIMO) system where base stations are equipped with several tens of transmit antennas and transmit data to multiple terminals (users) simultaneously. To enhance the performance of MU-MIMO systems, we, in this paper, propose an adaptive user selection algorithm which adaptively selects a user set according to varying channel states. According to Monte-Carlo based computer simulations, the performance of proposed scheme is significantly improved compared to the conventional scheme without user selection and approaches that of exhaustive search-based optimal scheme. On the other hand, the proposed scheme can reduce the computational complexity to $K/(2^K-1)$ compared to the optimal scheme where K denotes the number of total users.

• ETRI Journal
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• v.37 no.3
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• pp.450-459
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• 2015

Small cell networks, as an important evolution path for next-generation cellular networks, have drawn much attention. Different from the traditional base stations (BSs) always-on model, we proposed a BSs on-off model, where a new, simple expression for the probabilities of active BSs in a heterogeneous network is derived. This model is more suitable for application in practical networks. Based on this, we develop an analytical framework for the performance evaluation of small cell networks, adopting stochastic geometry theory. We derive the system coverage probability; average energy efficiency (AEE) and average uplink power consumption (AUPC) for different association strategies; maximum biased received power (MaBRP); and minimum association distance (MiAD). It is analytically shown that MaBRP is beneficial for coverage but will have some loss in energy saving. On the contrary, MiAD is not advocated from the point of coverage but is more energy efficient. The simulation results show that the use of range expansion in MaBRP helps to save energy but that this is not so in MiAD. Furthermore, we can achieve an optimal AEE by establishing an appropriate density of small cells.

• KIISE Transactions on Computing Practices
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• v.20 no.9
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• pp.519-524
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• 2014

The operating systems in the system architecture, which is integrated several applications and modular electronic devices in the same computing device, demand partitioning technology for safety. Thus, operation system requires partition scheduler for partition scheduling. When we design partition scheduler in embedded system, which has small memory and low performance, such as space system, we must consider not only performance but also memory. In this paper, we introduces a linux-based memory efficient partition scheduler using partition bitmap. This partition scheduler demands small memory space and produce low partition switching overhead. The prototype was executed on a LEON4 processor, which is the Next Generation Multicore Processor (NGMP) in the space sector. In evaluation, this prototype shows accuracy, additional memory space and low partition switching overhead.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.3
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• pp.60-67
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• 2011

Visible light communication system transmits data by controlling light emission of LED and receives data through photo detecter, which is considered as one of strong candidates of next generation wireless communication systems. The transmission capacity of visible light communication system depends on light intensity emitted from LED, sensitivity of PD, distance between transmitter and receiver, angle of incidence at the receiver. In particular, the receiver's vertical and horizontal movement changes distance between transmitter and receiver and angle of incidence, which may degrades transmission capacity of system. In this paper, we propose an estimation algorithm of receiver's position and angle based on tracking of received light intensity for indoor visible light communication systems. The performance evaluation of proposed algorithm confirms that the estimation algorithm of receiver's position and angle is quite important for visible light communication system to improve its transmission capacity.

• Journal of the Korea Computer Graphics Society
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• v.15 no.2
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• pp.35-40
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• 2009

In this paper, we present the web3D-based virtual reality(VR) system for the safety education of the hydrogen station. Currently, hydrogen is considered the next generation energy, and hydrogen station is a part of core infrastructure in hydrogen industry. However, the experience of safety equipment in the hydrogen station is limited to the non-experts, because it is a restricted area in general industry. Therefore, using the event driven method, we develop the VR system to transfer the information of hydrogen station to the non-experts. Using our system, user experiences the safety concerns in the hydrogen station, and also learn the informations of hydrogen energy.

• Journal of Advanced Navigation Technology
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• v.19 no.1
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• pp.22-32
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• 2015

Ground based augmentation system (GBAS) is a next generation radio navigation aids to support precision approach of aircraft. Recently, airports installing GBAS and providing GBAS service are increasing all over the world. For the first time in Korea, SLS-4000 which is the GBAS ground equipment of Honeywell had been installed at Gimpo International Airport in 2013, and evaluated its functionality and performance of through the ground testing. This paper introduces a ground test and evaluation criteria on the CAT-I GBAS system, and describes testing methods for GBAS ground testing of Gimpo International Airport. In addition, detail testing methods and analysis results on major five of 12 ground test items are described.

• The KIPS Transactions:PartC
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• v.11C no.7 s.96
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• pp.1023-1032
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• 2004

It is generally known that handoff delay degrades the QoS by packet drop, packet delay and jitter. Moreover. handoff highly effects on QoS in beyond 3G system because not only micro cells for achieving high capacity and fast moving nodes induce the frequent handoff but also hard handoff must be carried out in OFDM system. Therefore, study on a handoff algorithm for guaranteeing QoS is required. Related works on handoff for beyond 3G system mainly focused on reducing the L3 handoff delay or packet loss. That is, these schemes try to compensate L2 delay rather directly eliminate it. However, remained 1.2 delay degrades QoS, especially delay-sensitive realtime traffic. Therefore, we proposed the seamless handoff algorithmwhich can minimize the L2 handoff delay.